[Dissecting aneurysm of the middle cerebral artery with subarachnoid hemorrhage showing complete occlusion at the M2 portion of the middle cerebral artery on preoperative angiograms: case report].

We present a surgical case of a dissecting aneurysm of the middle cerebral artery associated with subarachnoid hemorrhage and intracranial hemorrhage. A 29-year-old man suddenly fell into a comatose state, and was referred to our hospital. CT scan showed diffuse subarachnoid hemorrhage and an intracerebral hematoma with marked midline shift located in the right frontal lobe. The right carotid angiogram revealed complete occlusion at the M2 portion of the middle cerebral artery, but failed to reveal any aneurysms in the rest of the intracranial circulation. We undertook emergent surgery to evacuate the hematoma and to confirm whether it was a dissecting aneurysm or not. After evacuation of the hematoma of the right frontal lobe, the Sylvian fissure was noticed to be widely opened. We detected a large dissecting aneurysm with a dark-purplish wall arising from the right M2 trunk, and we trapped the aneurysm. The postoperative course was uneventful and the patient gradually improved and was discharged without neurological deficits. We presented this case with a review of the literature.